Investigation on the microwave sintering of bio-material powders which have different calcium phosphate mineral structure

The main objective of this study was to investigate the microwave sintering properties and stability of two commercial calcium phosphate powders which have different mineralogical structure namely Hydroxyapatite HA (Ca10 (PO4)6 (OH)2) and ß-tri-calcium phosphate (ß-TCP, Ca3 (PO4)2). Hydroxyapatite and ß-tri-calcium phosphate are two widely used raw materials for the production of synthetic ceramic bone production. These materials are also used for the manufacturing of synthetic bone graft production. Pore structure and mineralogical constituents are major factors for the determination of the graft stability in body fluids and augmentation of bone cells in the graft material. For this reason, fast sintering (30-90 min) of these powders under microwave sintering conditions without changing their mineral structure and mineralogical stability is an important research field. In this study, 3 series of sample were prepared from HA, ß-TCP and equal amount mixture of these two powders according to dry pressing technique by using hydraulic press and steel die. Samples were sintered under microwave sintering conditions at 900 oC, 1000 oC and 1100 oC by holding 1 hour at maximum sintering temperature. Samples were allowed to cool in the furnace and taken from the furnace at room temperature. 5 oC/min heating rate was used for the sintering experiments. Bulk density, apparent porosity and strength of the samples were measured. XRD study was conducted on the samples before and after the sintering in order to determine the phase change. SEM investigations were done for the observation of microstructures and measurement of the pore sizes. As a conclusion, sintering properties of different calcium phosphate ceramics under microwave conditions were examined and it was found that mixture of HA and TCP powders is better properties of all for the production of synthetic graft material.